External reluctance solenoid



May 1, 1962 H. Y. FISHER EXTERNAL RELUCTANCE SOLENOID 3 Sheets-Sheet 1 Filed Feb. 24, 1959 ATT'YS May 1, 1962 H. Y. FISHER EXTERNAL RELUCTANCE SOLENOID 5 Sheets-Sheet 2 Filed Feb. 24, 1959 FIG? HARDIN Y FISHER II '0 Mw v ATT'YS FIG. 9

H. Y. FISHER EXTERNAL RELUCTANCE SOLENOID May 1, 1962 3 Sheets-Sheet 3 Filed Feb. 24, 1959 INVENTOR: HARDIN Y. FISHER FIG. I5

ATT'YS United States patent t.

3,032,694 EXTERNAL RELUCTANCE SOLENOID Hardin Y. Fisher, Hillside, Ill., assignor to Albert F. Dormeyer, Chicago, Ill. Filed Feb. 24, 1959, Ser. No. 795,261 23 Claims. (Cl. 317-186) This invention relates in general to solenoids, and more particularly to improvements in alternating current solenoids. It has been the desire of solenoid manufacturers to develop a solenoid having improved operating characteristics, including rugged construction resulting in longer life, good seal pull characteristics, quieter operation, and better pull curve characteristics. Accordingly, one of the objects of this invention is to provide a solenoid incorporating these improvements and others.

A further object of this invention resides in the provision of a solenoid having a C-frame construction which is quieter operating than solenoids heretofore developed.

Another object of this invention is in the provision of a solenoid having a specially designed C-frame with a small opening that positively supports the plunger slide whereby the plunger is centrally and squarely located at all times thereby assuring the plunger to accurately seat on the frame surfaces.

Still another object of this invention is to provide a solenoid having a specially designed C-frame which provides a low reluctance return path for the local flux produced by the current in the shading coils by providing a maximum cross sectional area path for this local return flux.

A still further object of this invention is in the provision of a solenoid having a good seal pull at relatively low flux densities without sacrificing excessive shading coil losses'when the solenoid is operated at high flux densities.

Another object of this invention is to provide a solenoid having a specially designed C-frame which prevents the solenoid pull from dropping too low when the plunger is in the extreme out position.

Still another object of this invention is to provide a solenoid having a specially designed C-frame and a plunger with an external permeable bar which reduces the reluctance of the solenoid magnetic circuit thereby increasing the pull of the solenoid as the plunger approaches its seated position.

A further object of this invention resides in the provision of an outstop spring for a solenoid which defines a spring cushion for the solenoid coil to absorb the coil inertia when the plunger strikes the frame upon seating.

A still further object of this invention is to provide an outstop spring for a solenoid which defines a rugged outstop for the plunger, wherein the spring stops the plunger over a short distance rather than abruptly thus greatly reducing the mechanical shock and the peening of parts.

Another object of this invention is to provide an antiresidual spring for a solenoid, wherein flexing of the spring is distributed over the entire length thereof thereby preventing fatiguing and breaking of the spring due to localized flexing and thus increasing the life of the spring.

A further object of this invention is to provide an antiresidual spring for a solenoid which may be changed without dismantling any part of the solenoid.

Still another object of this invention resides in the provision of a solenoid having an improved plunger slide structure which facilitates assembly of the solenoid and results in providing a more rigid and durable solenoid having a longer life.

Other objects, features, and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

Patented May 1, 1962 FIG. 1 is a perspective view of a solenoid embodying the invention;

FIG. 2 is an exploded view of the solenoid of FIG. 1;

FIG. 3 is a sectional view, taken substantially along lines 3-3 of FIGS. 1 and 6;

FIG. 4 is an enlarged view, partially fragmentary, taken substantially along lines 4-4 of FIG. 3 and illustrating the manner in which the outstop spring is arranged between the frame and the coil of the solenoid,

FIG. 5 is an enlarged sectional view taken substantially along lines 55 of FIG. 3;

FIG. 6 is a transverse sectional view or" the solenoid taken substantially along lines 66 of FIG. 3;

FIG. 7 is an exploded view of a solenoid similar to the solenoid in FIG. 1 but also including the antiresidual spring arrangement;

FIG. 8 is a sectional view of a solenoid of FIG. 7 in assembled form, taken substantially along lines 8--8 of FIG. 7;

FIG. 9 is a sectional view taken substantially along lines 9-9 of FIG. 8;

FIG. 10 is an enlarged view, partially fragmentary, taken substantially along lines lit-10 of FIG. 9 and illustrating the assembled positions of the outstop and antiresidual springs;

FIG. 11 is an enlarged view, partially fragmentary, taken substantially along lines 11--11 of FIG. 9;

FIG. 12 is a greatly enlarged sectional view, partially fragmentary, taken along lines 1212 of FIG. 9 and illustrating the positions of the outstop and antiresidual springs;

FIG. 13 is a sectional view, showing some parts in elevation, taken substantially along lines 1313 of FIG. 9;

FIG. 14 is a top plan view of the solenoid of FIG. 7 looking into the open end of the frame with the plunger removed; and

FIG. 15 is an elevational view of the solenoid according to the present invention, illustrating the specially designed C-frame and plunger, with the plunger in seated position.

To illustrate the invention, the drawings show the solenoid of the present invention as including generally a coil 16 having a plurality of turns carried on an insulating spool or bobbin 17 and a pair of terminal lugs 18 for connection to an electrical source.

A plunger 19 having an elongated narrow stem 20 is provided for the solenoid, wherein the stem is received inside the hollow of the spool for reciprocatory motion therewith. The plunger is constructed from a magnetically permeable material. A magnetically permeable C- shaped frame 21 embraces the coil 16 to increase the efficiency of the solenoid. The frame is constructed in the usual manner by securing together a plurality of identically formed laminae 22. On the opposite outer laminae is secured a specially formed lamina 23, FIG. 2, having spaced apart flanges 24 and 25 struck out therefrom for providing support and positioning of the coil 16 as seen in FIG. 1. The laminae 22 and 23 are secured together by a plurality of rivets 26.

The flanges 24 and 25 are cut away or notched at their inner edges at 27 and 28, FIG. 2, to provide clearance for receiving the identical but oppositely facing plunger slides 29 and 30. These slides are made of nonpermeable material.

Referring now particularly to FIG. 15, it will be noted that the C-shaped frame 21 includes parallel spaced legs 31 and 32 straddling the coil =16 and being connected together at adjacent ends by the bight 33 of the frame. At the other ends of the legs, inwardly extending projections 34 and 35 are provided which have substantially the same cross section as the legs of the frame. Narrow projections 36 and 37 extend inwardly from the projections 34 and 35, respectively, and define therebetween an air gap or opening through which the plunger stem 26 passes. The very free ends of the projections 36 and 37 are arranged in close proximity to the adjacent sides of the plunger stem 20, as seen in FIG. 15. The projections 36 and 37 define with the inner end faces 38 and 39 of the projections 34 and 35 a reluctance gap between the faces 33 and 39 externally of the frame opening.

A pair of shading coils 40 and 41, FIG. 14, are arranged on the projections 34- and 35 of the frame. Each coil is constructed of a conductive material and formed in the shape of a rectangular loop having opposite sides 42 and 43 extending transverse to the frame laminae and embedded in slots 44 and 45, FIG. 15, formed in the outer surface of the projections 34 and 35. The other two sides 46 and 47 of each coil are arranged exteriorly of the frame as seen in FIG. 14.

Accordingly, the coils define a shaded area at each side of the frame, and the coils are arranged in a plane passing transversely through the plunger stem. The shaded areas defined by the coils are spaced outwardly of the opening or air gap defined by the projections 36 and 37, thereby leaving an unshaded portion of the frame at each side of the opening and directly adjacent thereto. Thus the greater portion of each projection 34 and 35 is shaded by the coils 4t and 41, while a small portion adjacent to the free end of these projections and the projections 36 and 37 define the unshaded areas of the frame. It may be noted that the shaded areas of the projections 34 and 35 extend a greater distance outwardly of the frame than the unshaded areas of these projections. The shaded areas, which may be designated by the numerals 48 and 49, together with the unshaded areas adjacent the free ends of projections 34- and 35 define the contacting or engaging areas which engage the seating bar 50 of the plunger 19.

The plunger 19 is also constructed from a plurality of laminae 51, FIG. 2, having arranged over the outer laminae pull bars 52, FIG. 2, and the pull bars and laminae are held together by rivets S3. The seating bar 50 is substantially rectangular in shape and extends transverse to the plunger stem 19 and has seating areas 54 and 55 which contact the shaded areas 48 and 49 and unshaded areas of the frame when the plunger is in seated position. The plunger is also provided with an external permeable bar 56 integral with the seating bar 50 and adjacent the inner side thereof. The permeable bar is also substantially rectangular in shape, being longer than the frame opening but of less length than the seating bar 50. The permeable bar is freely received in the external reluctance gap when the plunger is in seated position, but the bottom of the reluctance bar does not contact the projections 36 and 37 and the ends of the bar do not contact the faces 38 and 39 of the projections 34 and 35. It may be noted in FIG. 15, where the plunger is in closed or seated position, the seating bar of the plunger contacts the shaded areas 48 and 49 and the unshaded areas adjacent the free ends of projections 34 and 35. The inwardly extending projections 36 and 37 function to increase the unshaded areas and reduce shading coil losses at high flux densities. The narrow projections defining the opening in the frame thereby provide a low reluctance return path for the local flux produced by the current in the shading coils by providing a maximum cross sectional area path for this local return flux. Accordingly, the frame of the present invention provides a solenoid having -a good seal pull at relatively low flux densities without excessive shading coillosses when the solenoid is operated at high flux density.

As already explained, the reluctance gap in the magnetic circuit of the frame is filled by the external permeable bar of the plunger as the plunger approaches seated position whereby the reluctance of the magnetic circuit of the solenoid is reduced thereby increasing the 4 pull of the solenoid as the plunger approaches its seated position.

The two pull bars 52 of the plunger 19 are apertured and reinforced at their outer ends and define a pull bar through which the tractive force of the plunger may be exerted.

Referring particularly to FIG. 2, a pair of coil retaining and plunger outstop springs 57 are arranged between the flanges 24 and the adjacent end of the coil 16, wherein the springs abut against the outer flange 58 of the coil 16. The inner flange 59 of the coil bears against the flanges 25 at the other end of the frame 21. These springs are L-shaped, and when arranged between the flanges 24 and the coil 16 define a right angle polygon as seen in FIG. 3. Each spring includes a first leg 60 and a second leg 61. I

The first leg 66 engages at its free end the flange 24, FIG. 4, while the other end of the leg bears against the outer flange 58 of the coil. The leg 61 extends perpendicular to the leg 60, having the end connecting to the leg 60 bearing against the outer flange 58 of the coil as seen in FIG. 5. The other end of the leg 61. also bears against the coil flange 58, while the intermediate portion is arched and engages in pressing relation the under side of one of the projections 34 or 35 of the frame 21.

In order for this spring to limit the protracted position of the plunger, it is provided with an outstop 62 on the leg 60 which projects through an opening 63 provided in either of the slides 29 and 30, FIG. 2, and extends into the path of outstop lugs 64 struck out from the pull bars on the plunger. As seen in FIG. 6, the outstop lugs 64 will engage the outstops 62 when the plunger 19 is in the protracted position.

As may be seen in FIGS. 4 and 6, the outstops 62 project through the openings 63 at the end thereof adjacent the coil, whereby the outstops may flex toward the free ends of the plunger slides when the plunger is stopped in the protracted position thereby absorbing the inertia of the plunger.

The plunger outstop and coil retaining springs 57 are assembled with the other solenoid parts after positioning of the coil within the frame by insertion of a spring at each side of the solenoid between the flanges 24 and the spool 17 of the coil. In order to assure that the springs will remain in position during continued operation, a lug 65 is struck from each spring and from the free end of the leg 69, which lug snaps into an aperture 66, FIG. 5,

formed in the flanges 24. Thus, the springs are firmly locked in place, although they may be removed by bending the free end of the leg 60 toward the coil and pulling the spring out of the solenoid.

The coil retaining and plunger outstop springs 57 provide a spring cushion for the coil to absorb its inertia when the plunger strikes the frame in seating. Accordingly, this inertia is absorbed by the frame laminations and not by other parts of the solenoid due to this mechanical shock. 1

Further, the coil retaining and outstop springs define rugged outstops for the plunger and the resiliency of the outstop stops the plunger by absorbing the energy rather than just withstanding it and causing mechanical shock and the peening of the parts. If a stronger outstop is desired the thickness of the material may be increased.

Referring now particularly to FIGS. 7, 8, 9, 10', ll, 12 and 13, a pair of antiresidual springs 67 may be positioned between the flanges 2.4 of the frame and the coil retaining and plunger outstop springs 57 in order to counteract the residual magnetism present in the solenoid when the plunger is seated. The antiresidual springs are L-shaped and positioned in the solenoid as seen in FIG. 9 in superimposed relation with the coil retaining and plunger outstop springs 57. Each antiresidual spring includes a leg 68 substantially identical with the leg 61 of each coil retaining and outstop spring 57. The contour of the leg 63 simulates that of the leg 61 of the coil retaining outstop spring as seen in FIG. 10. Connected to the leg 68 of each spring and at right angles thereto is a leg 69 having a stop 7% which extends through the plunger guide opening 63 in spaced relation from the plunger outstop 62 as seen most clearly in FIGS. 12 and 13. The plunger stem has antiresidual spring lugs 71 protruding from opposite sides, as seen in FIGS. 7 and 8, which strike and depress the antiresidual stops 70 when the plunger is in seated position.

The leg 68 of each antiresidual spring is notched at its free end at each side as indicated by the numeral 72 in FIG. 7 to receive upwardly struck positioning flanges 73 of each coil retaining and plunger outstop spring, FIG. 7, for the purpose of properly positioning the antiresidual springs in the solenoid. Additionally, each antiresidual spring is notched at 74 to receive a positioning flange 7'5 struck from the coil retaining and outstop spring '57. The three positioning flanges on the coil retaining and plunger outstop spring serve to lock the antiresidual spring in proper position and prevent any relative movement therewith. It is a simple matter to add the residual springs in the solenoid by merely positioning them relative to the coil retaining and outstop springs and inserting both springs at the same time in the solenoid.

The coil retaining and outstop springs and residual springs will be made of spring steel, and will last the life of the solenoid. However, it may be appreciated that the springs can be easily changed without completely dismantling the solenoid. And for different applications the force exerted by the springs may be changed by increasing or decreasing the material thickness.

The flexing of the antiresidual spring is distributed over the entire length of the spring thereby preventing fatiguing and breaking of the spring due to localized flexing. Since this spring will last the life of the solenoid, it will be of good use since it is at the end of the solenoid life that the spring is most needed, because the demagnetizing air gap at the end of the plunger closes up as the solenoid wears, thereby causing the residual magnetism to increase as the seating surfaces wear.

The plunger slides 29 and 30 are constructed so that they may be inserted into place within the coil when assembling the solenoid and locked into place without resorting to the use of any special tools. Referring to FIG. 2, each plunger slide is seen to be identical in size and shape but facing each other to define a track for reciprocably receiving the stem of the plunger. Since each plunger slide is the same, only one need be specifically described and, accordingly, the numerals applied may be similarly applied to the same parts of the other slide.

Each slide includes an elongated body portion 76 having a pair of flanges 77 bent at right angles thereto at each side. The flanges extend substantially along the entire length of the body portion. The body portion, when arranged in the solenoid, extends parallel to the longitudinal axis of the frame, while the flanges 77 extend transverse to the longitudinal axis of the frame. A depressed channel portion 78 extends substantially throughout the entire length of the body portion 76 defining a clearance for the lugs 64 and 71 of the plunger stem. The opening 63 is cut in this channel and receives the stops from the coil retaining and outstop springs and the antiresidual springs when the solenoid is assembled.

In order to stabilize the plunger slides in assembled position, the outer laminae at each side of the frame is provided with stabilizing bars 79 at each side of the opening, FIG. 2, 11, 13 and 14. The stabilizing bars abut against the outer surfaces of the slide flanges 77, FIG. 14, and thereby prevent movement of the flanges at the outer end along a plane extending parallel to the longitudinal axis of the frame. In order to prevent movement of the outer ends of the slides along a plane extending perpendicular to the longitudinal axis of the frame, cars 80 extend from the slides in abutting relation with the outer surfaces of the stabilizing bars 79, and ears 81 ex tend from the stabilizing bars and in abutting relation with the outer surfaces of the body portion of each slide, as seen in FIGS. 11, 13 and 14. Accordingly, a more rugged plunger slide structure is provided which is less susceptible to being displaced or damaged by any oscillating movement of the plunger when it is in protracted position.

At the outer ends of each slide the flanges 77 are notched at 82, FIG. 2, in order to provide clearance for the seating bar 50 and external permeable bar 56 of the plunger when the plunger is in seated position. The inner ends 33 of the slide flanges 77 bottom the flanges against the bight 33 of the frame, while extensions 84 of the body portions 76 lie along the outer surfaces of the frame bight 33 as seen in FIG. 13. If desired, a rivet may be extended through these extensions and the frame in order to positively secure the slides in position. However, in order to prevent longitudinal movement of the slides, it may be seen in FIG. 13 that the outstops 62 which extend through the openings 63 of the slides firmly hold the slides in assembled position. If the extensions 84 are not riveted to the frame, it may be appreciated that the slides can be inserted into the solenoid quickly and easily while assembling and thereby eliminate the necessity of a special operation. Additionally, the slides may be changed if desired without completely dismantling the entire solenoid, and without removal of any rivets.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is claimed as follows:

1. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow cen ter of the coil, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stern reciprocates, said opening being only slightly wider than said stem, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular external permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, and recesses in the frame at each side of the opening defining an external reluctance gap which receives said external permeable bar when the plunger is in seated position.

2. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, said opening being only slightly wider than said stem, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular external permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, and recesses in the frame at each side of the opening defining an external reluctance gap which receives said external permeable bar when the plunger is in seated position, and a pair of loop-shaped shading coils embedded in slots in the frame, each coil surrounding the seating area on the frame which contacts the seating bar of the plunger on each side of the opening, said coils defining a shaded area at each side of the frame and spaced outwardly of said opening, while leaving the areas immediately adjacent the opposite sides of the opening unshaded, the surfaces of said unshaded frame areas being the same height as the unshaded area so the plunger seats on both surfaces.

3. In a solenoid, a coil with a hollow center, a plunger 7 having an elongated stem reciprocable in the hollow cenwider than'said stem, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular external permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, and recesses in the frame at each side of the opening defining an external reluctance gap which receives said external permeable bar when the plunger is in seated position, and means for shading an area of the frame at each side of the opening, whereby said shaded areas define the seating areas on the frame which contact the seating bar of the plunger when the plunger is in seated position, said shaded areas being spaced outwardly from the opening thereby leaving the frame areas immediately adjacent the opening unshaded.

4. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocab-le in the hollow center of the coil, a substantially C-shaped frame embracing said winding with the legs of the C extending transverse to the turns of the coil, a first projection extending inwardly from the free end of each leg of the C and substantially perpendicular thereto, a second projection extending inwardly from the free ends of said first projections and defining an opening through which the plunger stem reciprocates, the free ends of said second projections terminating closely adjacent the opposed sides of the plunger stem, said second projections having a cross section greatly reduced from said first section and defining therewith recesses in the frame on opposite sides of the opening and a reluctance gap externally of said opening, a seating bar on said plunger adapted to engage the frame on either side of said opening whe nthe plunger is in seated position, a generally rectangular permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially Wider than said stem, said permeable b-ar being received in said reluctance sgap when the plunger is in seated position.

5. Ina solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a substantially C-shaped frame embracing said winding with the legs of the extending transverse to the turns of the coil, a first projection extending inwardly from the free end of each leg of the C and substantially perpendicular thereto, a secondprojection extending inwardly from the free ends of said first projections and defining an opening through which the plunger stem reciprocates, the free ends of said second projections terminating closely adjacent the opposed sides of the plunger stern, said second projections having a cross section greatly reduced from said first section and defining therewith recesses in the frame on opposite sides of the 7 opening and a reluctance gap externally of said opening,

a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, said permeable bar being received in said reluctance gap when the plunger is in seated position, and means for shading an area of the frame at each side of the opening, said shaded areas being spaced outwardly from said opening thereby leaving the frame areas immediately adjacent the opening unshaded.

6. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a substantially C-shaped frame embracing said winding with the legs of the 6 extending transverse to the turns of the coil, a firstprojection extending inwardly from the free end of each leg of the C and substantially perpendicular thereto, a second projection extending inwardly :from the free ends of said first projections and defining an opening through which the plunger stem reciprocates, the free ends of said second projections terminating closely adjacent the opposed sides of the plunger stern, said second projections having a cross section greatly reduced from said first section and defining therewith recesses in the frame on opposite sides of the opening and a reluctance gap externally of said opening, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stern, said permeable bar being received in said reluctance gap When the plunger is in seated position, and means for shading an area of the frame at each side of the opening, said shaded areas being spaced outwardly from said opening thereby leaving the frame areas immediately adjacent the opening unshaded.

'7. in a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a substantially C-shaped frame embracing said winding with the legs of the 0 extending transverse to the turns of the coil, a first projection extending inwardly from the free end of each leg of the G and substantially perpendicular thereto, a second projection extending inwardly from the free ends of said first projections and defining an opening through which the plunger stem reeiprocates, and free ends of said second projections terminating closely adjacent the opposed sides of the plunger stem, said second projections having a cross section greatly reducedfrom said first section and defining therewith recesses in the frame on opposite sides of the opening and a reluctance gap externally of said opening, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, said permeable bar being received in the reluctance gap when the plunger is in seated position, anda pair of shading coils on said frame, each coil comprising a substantially rectangular loop of conductive material lying in a plane parallel to the longitudinal axes of said projections and defining shaded areas spaced outwardly of said opening, whereby the frame areas immediately adjacent the opening are unshaded, said shaded areas together with unshaded areas. constituting the seating areas of the frame upon which the seating bar rests when the plunger is in seated position.

8. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a substantially C-shaped frame embracing said Winding with the legs of the C extending transverse to the turns of the coil, a first projection extending inwardly from the free end of each leg of the t3 and substantially perpendicular thereto, a second projection extending inwardly from the free ends of said first projections and defining an opening through which the plunger stem reciprocates, the free ends of said second projections terminating closely adjacent the opposed sides of the plunger stern, said second projections having a cross section greatly reduced from said first section and defining therewith recesses in the frame on opposite sides of the opening and a reluctance gap externally of said opening, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, said permeable bar being received in said reluctance gap when the plunger is in seated position, and a pair of shading coils on said frame, each coil comprising a substantially rectangular loop of conductive material lying in a plane parallel to the longitudinal axes of said projections and defining shaded areas spaced outwardly of said opening, whereby the frame areas-immediately adjacent the opengreases ing are unshaded, said shading areas together with unshaded areas constituting the seating areas of the frame upon which the Seating bar rests when the plunger is in seated position.

9. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, said opening being only slightly wider than said stem, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a generally rectangular external permeable bar adjacent said seating bar, said permeable bar being substantially narrower than said seating bar and substantially wider than said stem, and recesses in the frame at each side of the opening defining a reluctance gap externally of said opening for receiving said external permeable bar when the plunger is in seated position, and a pair of shading coils on said frame, each coil comprising a substantially rectangular loop of conductive material lying in a plane parallel to the longitudinal axes of said projections and defining shaded areas spaced outwardly of said opening, whereby the frame areas immediately adjacent the opening are unshaded, said shaded areas together with unshaded areas constituting the seating areas of the frame upon which the seating bar rests when the plunger is in seated position.

10. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, outstop lugs on the plunger adjacent the inner end thereof, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stern reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil sup-porting flanges at each side of said frame between which the coil is posi- L tioned, and a pair of L-shaped coil retaining and plunger outstop springs arranged between one end of the coil and the adjacent coil supporting flanges, whereby the coil is thereby resiliently biased toward the other coil supporting flanges, each spring having an outstop thereon in the path of an outstop lug, thereby limiting the protracted position of the plunger.

11. In a solenoid, a coil with a hollow center, a plunger having an elongated stern reciprocable in the hollow center of the coil, outstop lugs on the plunger adjacent the inner end thereof, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of, outwardly extending coil supporting flanges at each side of said frame between which the coil is positioned, and a pair of L-shaped coil retaining and plunger outstop springs arranged between one end of the coil and the adjacent coil supporting flanges, whereby the coil is thereby resiliently'biased toward the other coil supporting flanges, each spring having an outstop thereon in the path of an outstop lug, thereby limiting the protracted position of the plunger, and means on said springs coacting with means onsaid flanges for locking the springs in retained position.

12. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, outstop lugs on the plunger adjacent the inner end thereof, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said frame between which the coil is positioned, and a pair of L-shaped coil retaining and plunger outstop springs arranged between one end of the coil and the adjacent coil supporting flanges, whereby the coil is thereby resiliently biased toward the other coil supporting flanges, each spring having :a pair of legs perpendicularly connected together to form the L-shape, one of said legs positioned between a flange and the coil and having a contour whereby the free end presses against the flange and the end connected to the other leg presses against the coil, the outstop being carried by said leg, the other leg having its opposite ends pressing against the coil and its intermediate portion pressing against a part of the frame.

13. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, outstop lugs on the plunger adjacent the inner end thereof, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said frame between which the coil ispositi'oned, and a pair of L-shaped coil retaining and plunger outstop springs arranged between one end of the coil and the adjacent coil supporting flanges, whereby the coil is thereby resiliently biased toward the other coil supporting flanges, each spring having a pair of legs'perpendicularly connected together to form the L-shape, one of said legs positioned between a flange and the coil and having a contour whereby the free end presses against the flange and the end connected to the other leg presses against the coil, the outstop being carried by said leg, the other leg having its opposite ends pressing against the coil and its intermediate portion pressing against a part of the frame, each spring having an outstop thereon inthe path of an outstop lug, thereby limiting the protracted position of the plunger.,

14. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, outstop lugs on the plunger adjacent the inner end thereof, a frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said frame between which the coil is positioned, and a pair of L-shaped coil retaining and plunger outstop springs arranged between one end of the coil and the adjacent coil supporting flanges, whereby the coil is thereby resiliently biased toward the other coil supporting flanges, said springs arranged to form a right angle polygon, each spring having an outstop thereon in the path of an outstop lug, thereby limiting the protracted position of the plunger.

15. In a solenoid, a coil with a hollow center, a plunger having an elongated stern reciprocable in the hollow center of the coil, a right-polygonally shaped frame embracing said coil, antiresidual lugs on said plunger adjacent the outer end thereof, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said i 1 adjacent the outer end thereof, a said frame having a narrow opening at one end through which the plunger stern reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said frame between which the coil is positioned, means biasing said coil against the flanges at one end of said frame, and a pair of L-shaped antiresidual springs arranged between the outer end of the coil and the adjacent flanges, each spring having a stop extending into the path of an antiresidual lug thereby applying a slight force to said plunger in the direction away from the frame when the plunger is in seated position.

17. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a right-polygonally shaped frame embracing said coil, antiresidual lugs on said plunger adjacent the outer end thereof, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges ateach side of said frame between which the coil is positioned, a pair of L-shaped coil retaining springs arranged between the outer end of the coil and the adjacent flanges, whereby the coil is resiliently biased toward the closed endof the frame, means locking said coil retaining springs to said flanges, and a pair of L-shaped antiresidual springs arranged between said coil retaining springs and-said flanges, each antiresidual spring having a stop extending into the path of an antiresidual lug and being positioned to apply a slight force against the-plunger toward unseated position when the plunger is in seated position.

18. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a right-polygonally shaped frame embracing said coil, antiresidual lugs on said plunger adjacent the outer end thereof, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair if outwardly extending coil supporting flanges at each side of said frame between which the coil. is positioned, a pair of L-shaped coil retaining springs arranged between the outer end of the coil and the adjacent flanges, whereby the coil isresiliently biased toward the closed end of the frame, means locking said coil retaining springs to said flanges, and a pair of L-shaped antiresidual springs arranged between said coil retaining springs and said flanges, means on said coil retaining springs for locking said antiresidual springs thereto, each antiresidual spring having a stop extending into the path of an antiresidual lug and being positioned to apply a slight force against the plunger toward unseated position when the plunger is in seated position.

19. In a solenoid, a coil with a hollow center, a plunger having an elongated stern reciprocable in the hollow center of the coil, a right-polygonally shaped frame embracing said coil, outstop lugs on the plunger adjacent the inner end thereof, antiresidual lugs on said plunger adjacent the outer end thereof, said frame having'a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted toengage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil supporting flanges at each side of said frame between which the coil is positioned, a pair of L-shaped coil retaining and plunger outstop springs arranged between the outer end of the coil and the adjacent flanges, whereby the coil is resiliently biased toward the closed end of the frame, means locking said coil retaining and plunger outstop springs to said flanges, each spring having an outstop thereon in the path of an outstop lug, thereby limiting the protracted position of the plunger, and a pair of L-shaped antiresidual springs arranged between said coil retaining and plunger outstop springs and said flanges, means on said coil retainer and plunger outstop springs for locking said antiresidual springs thereto, each antiresidual spring having a stop extending into the path of an antiresidual lug thereby applying a slight force to said plunger in the direction away from the frame when the plunger is in seated position.

20. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a right-polygonally shaped frame embracing said coil, outstop lugs on the plunger adjacent the inner end thereof, antiresidual lugs on said plunger adjacent the outer end thereof, said frame having a narrow opening at one end through which the plunger stem reciprocates, a seating bar on said plunger adapted to engage the frame on either side of said opening when the plunger is in seated position, a pair of outwardly extending coil sup porting flanges at each side if said frame between which the coil is positioned, a pair of L-shaped coil retaining and plunger outstop springs arranged between the outer end of the coil and the adjacent flanges, whereby the coil is resiliently biased toward the closed end of the frame, means locking said coil retaining and plunger outstop springs to said flanges, each spring having an outstop thereon in the path of an outstop lug, hereby limiting the protracted position of the plunger, and a pair of L-shaped antiresidual springs arranged between said coil retaining and plunger outstop springs and said flanges, means on said coil retaining and plunger outstop springs for locking said antiresidual springs thereto, each antiresidual spring having a stop extending into the path of an antiresidual lug thereby applying a slight force to said plunger in the direction away from the frame when the plunger is in seated position, each antiresidual spring having a pair of legs perpendicularly connected together to form the L-shape, one of said legs carrying the antiresidual stop and being spaced from the coil retaining and outstop spring and the other leg resiliently wedging the spring between the coil retaining and outstop spring and a part of the frame.

21. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reeiprocable in the hollow center of the coil, a laminated C-shaped frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem re'ciprocates, said open ing being only slightly wider than said stern, a plunger slide structure including a pair of spaced identically shaped nonpermeable slides extending through the hollow of the coil and the opening of the frame, each slide having a main body extending parallel to a side of said plunger and in closely spaced relation therewith for limiting movement of the plunger along a plane extending transverse to the longitudinal axis of the frame, a pair of slide flanges extending perpendicularly from each edge of said body and along substantially the entire length thereof for limiting movement of the plunger along a plane extending parallel to the longitudinal axis of the frame, and stabilizing bars extending from the outer laminae of the frame adjacent said opening and into engagement with the outer surfaces of said slide flanges thereby preventing movement of the slides along a plane extending parallel to the longitudinal axis of the frame.

22. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a laminated C-shapedframe embracing said coil, said frame having a narrow opening at one end through which the plunger stern reciprocates, said opening being only slightly wider than said stem, a plunger slide structure including a pair of spaced identically shaped nonpermeable slides extending throughthe hollow of the coil and the opening of the frame, each slide having a main body extending parallel to a side of said plunger and in closely spaced. relation therewith for limiting movement of the plunger along a plane extending transverse to the longitudinal axis of the frame, a pair of slide flanges extending perpendicularly from each edge of said body and along substantially the entire length thereof for limiting movement of the plunger along a plane extending parallel to the longitudinal axis of the frame, stabilizing bars extending from the outer laminae of the frame adjacent said opening and into engagement with the outer surfaces of said slide flanges thereby preventing movement of the slides along a plane extending parallel to the longitudinal axis of the frame, and means on said slides and said stabilizing bars preventing movement of the slides along a plane perpendicular to the longitudinal axis of the frame.

23. In a solenoid, a coil with a hollow center, a plunger having an elongated stem reciprocable in the hollow center of the coil, a laminated C-shaped frame embracing said coil, said frame having a narrow opening at one end through which the plunger stem reciprocates, said opening being only slightly wider than said stem, a plunger slide structure including a pair of spaced identically shaped nonpermeable slides extending through the hollow of the coil and the opening of the frame, each slide having a main body extending parallel to the side of said plunger and in closely spaced relation therewith for limiting movement of the plunger along a plane extending transverse to the longitudinal axis of the frame, a pair of slide flanges extending perpendicularly from each edge of said body and along substantially the entire length thereof for limiting movement of the plunger along a plane extending parallel to the longitudinal axis of the frame, stabilizing bars extending from the outer laminae of the frame adjacent said opening and into engagement with the outer surfaces of said slide flanges thereby preventing movement of the slides along a plane extending parallel to the longitudinal axis of the frame, and means on said slides and said stabilizing bars preventing movement of the slides along a plane perpendicular to the longitudinal axis of the frame, said last named means comprising ears on said slides abutting against the outer surfaces of said stabilizing bars and ears on said stabilizing bars butting against the outer surfaces of said slides.

References Cited in the file of this patent UNITED STATES PATENTS 2,348,556 Matthias May 9, 1944 2,516,603 Soreng et a1 July 25, 1950 2,715,199 Bogue et a1 Aug. 9, 1955 2,812,479 Seitzman Nov. 5, 1957 2.899.609 Andrews Aug. 11, 1959 

